Polymerization of olefins can be carried out by the solution process or by the particle form process. In both processes, the polymerization generally occurs in a polymerization zone in the presence of a suitable catalyst and a hydrocarbon diluent. After polymerization, the polymerization effluent contains polymer, either in solution form or in particle form, depending upon the process employed, and hydrocarbon diluent.
It is desirable for reasons of economy to return the hydrocarbon diluent and/or unreacted monomer(s) to the polymerization zone after separating such from the polymer product. However, difficulties are encountered. For one thing, it is generally desirable for reasons of product quality and control of the polymerization process to inactivate the residual catalyst which can be contained in the polymerization effluent. In this event, however, special precautions must be taken to prevent the catalyst inactivating agent from returning to the polymerization zone where the unactivated catalyst can have a deleterious effect on the polymerization control and can cause blocking of process lines and similar problems in downstream equipment. In the case of organometal compounds another problem encountered is that such active organometal compounds remaining in the polymer product can be pyrophoric and can ignite on exposure to oxygen. Hence, it is necessary to deactivate such organometal compounds before drying the polymer.
It is also highly desirable to deactivate the polymerization zone effluent as soon as possible after leaving the polymerization zone both to maintain even quality of the polymer and to prevent downstream problems such as those delineated above, for example, blocking of process lines and equipment and potential fire hazards. In many polymerization systems, the unreacted monomer(s) and polymerization diluents can be removed from the polymer product, for example, by flashing or vaporization, and returned to the polymerization zone. Methods known in the prior art for deactivating active catalyst residues prior to this recycle point have suffered from serious disadvantages. Typically, such catalyst deactivation steps have involved treatment with agents such as water, wet nitrogen, alcohols, low boiling epoxides, carbon dioxide, and the like. However, such agents can be carried back with the recycled monomer(s) and diluents, and can cause poisoning of the catalyst in the polymerization zone of the process. Accordingly, it is highly desirable that a catalyst deactivation process be capable of deactivating the residual active catalyst in polymerization zone effluent as soon as possible after polymerization without being returned to the polymerization zone. Another problem encountered in prior art methods for deactivating residual active catalyst in polymerization zone effluent is that if the treating compound contains active hydrogen, such as, for example, alcohols, amines, wet gases, and the like, hydrogen chloride can be liberated during the deactivation treatment causing corrosion problems with the polymerization process equipment. Accordingly, it is highly desirable that a catalyst deactivation process not liberate HCl while being at the same time capable of deactivating polymerization zone effluent as soon as possible after leaving the polymerization zone.
Further, as is known in the art, it is frequently desirable to add to the polymer product stabilizing agents for stabilizing the polymer product against such as thermal degradation, ultraviolet degradation, and the like.